The present invention pertains to air breathing heat engines such as combustion turbines, and, in particular, to a system for cooling the acoustic enclosure or housing for the heat engine.
The aero-derivative and framed combustion turbine (CTs) are rapidly becoming the power generator of choice. Earlier applications of CTs were configured to meet spikes in energy dispatch and with very little regard for heat rates. Due to many favorable features of CTs such as their being relatively environmental friendly, as well as their improvement in heat rates and reduced capital costs, CTs are increasingly being employed in intermediate and base load generation and now likely will be the wave of the foreseeable future.
In a stationary power generation mode, CT housings or enclosures are designed to absorb sound energy achieving free-field noise emissions levels not exceeding 63 decibels at 200 feet and to provide for weather protection. These enclosures are structured around the power take-offs, hot section of the turbine, combustors, and the compressors. These engine components within the enclosure radiate, convect, and conduct heat at the rate of the thermal loss expressed as the over-all energy transformation efficiencies which can be calculated: EQU (output/input).times.100=thermal efficiencies
Typical CT thermal efficiency are such that they radiate 25-35% of the heating value of the fuel burned which is conducted and convected into the acoustic enclosure.
One problem with existing acoustic enclosures is their tendency to retain the heat being produced by the engine components. In particular, all things being equal, turbines surrounded by high temperature air operate less efficiently than turbines surrounded by cooler air. Although some of the heat produced in energy transformation by the turbine is removed by oil cooling systems and engine exhausts, an appreciable amount of heat is transferred to the enclosure and the air contained therein. This transferred heat causes the air in the enclosure to increase in temperature, which tends to adversely affect turbine efficiency.
To offset the radiated energy from the operating turbine which is conducted from the turbine case and power take-off to the entrapment within the enclosure, ambient filtered air at a rate between 10-20 cfm per kilowatt of the turbine has previously been forcibly vented by blowers through the enclosure as a coolant. However, the cooling capabilities of such a configuration is less than desired.
Thus, it would be desirable to provide a better cooling system for the interior volume of an acoustic enclosure to further enhance combustion turbine efficiency.